Contact lens technology is nearly three decades old and superficially would seem to be well developed. For example, a great many polymeric materials have been evaluated for potential utility as contact lens material. A very limited number of materials have, however, found their way into contact lenses which are satisfactory in all respects. Notwithstanding a large reservoir of experience, advances in contact lens materials and techniques have come a small steps. Even small steps have been excruciatingly slow and difficult, and polymers and methods which initially appeared very attractive have fallen by the wayside on the long and difficult journey from initial efforts to ultimate user acceptance. The problems are myriad and predictability as to ultimate lens acceptability based upon polymer characteristics is low. It is, for example, difficult at best, and frequently impossible, to predict optical quality, strength and flexibility, resistance to protein build-up, machining and fabrication characteristics, dimensional stability, oxygen permeability, and general biological compatability. The following survey of prior art efforts involving the generic class of compounds of interest, silicones, is not represented to be complete, but includes the disclosures known to and considered by the inventor as being most relevant to the present invention.
Reference is first made to the voluminous literature, in texts, treatises and technical literature which describe siloxyl compounds, commonly referred to as silicones. While the present invention departs from this chemistry in important and substantial ways, insofar as lens technology is concerned, this body of chemistry is fundamental to the present invention.
Merkler, U.S. Pat. No. 2,922,807, discloses disiloxanes of the formula ##STR1## wherein n is an integer from 1 to 4, R is hydrogen or methyl and R is a monovalent hydrocarbon radical free of aliphatic unsaturation.
Merker, U.S. Pat. No. 2,956,044, describes acryloxymethylsilicon polymers of siloxanes, a simple but representative example of which is: EQU CH.sub.2 .dbd.CRCOOCH.sub.2 SiR'.sub.3
wherein R is hydrogen or methyl and R' is a monovalent hydrocarbon radical. A great many examples of monomers and polymers are given, vinyl polymerizing conditions for forming such polymers is described in some detail and examples are given. The resulting products ranged from liquids, coating agents, adhesives, and bonding agents to thermoplastic and thermoseting resins.
Lamereaux, U.S. Pat. No. 3,197,433, disclosed optically clear organopolysiloxane resins. These, and earlier, resins had been proposed for use in optical contact lenses.
Becker, U.S. Pat. No. 3,228,741, disclosed a corneal contact lens fabricated from transparent silicone rubber. This was what might be called a "soft" contact lens and is said to have had an oxygen permeability higher than conventional lenses extant at that time.
Gaylord, U.S. Pat. No. 3,808,178, and U.S. Pat. No. 4,120,570 discloses oxygen permeable contact lenses fabricated from a copolymer of polysiloxanylalkyl acrylic ester and an alkyl acrylic ester. The polysiloxanylalkyl ester monomer has the structural formula ##STR2## wherein X and Y are C.sub.1 -C.sub.5, phenyl or groups of the structure ##STR3## m being an integer from 1 to 5, n being an integer from 1 to 3, and wherein A is selected from C.sub.1 -C.sub.5 alkyl and phenyl groups, and R is methyl or hydrogen. Gaylord does not disclose, or suggest, other than polysiloxanyl-alkyl esters, as the silicone constituent of his lenses. In particular reference to the present invention, there is neither disclosure nor suggestion of silicone hydride compositions.
Merrill, U.S. Pat. No. 4,099,859, discusses the omnipresent problem of wettability silicone based contact lenses and proposes a rather complex solution to the challenge of incorporating adequate wettability, for comfort and biological compatability, into a silicone lense without giving up the oxygen permeability of the silicone polymer. According to Merrill's method, which is not known to have found widespread use, a thin layer of optically clear hydrophilic polymer is grafted to the silicone lens, using a high dose of ionizing radiation to prepare the silicone base material. One would expect such a lens to be exceedingly expensive and fragile.
Chen, U.S. Pat. No. 4,143,949 discloses a somewhat similar approach to that taken by Merrill, U.S. Pat. No. 4,099,859, in using a plasma glow discharge to prepare a silicone lens to accept a hydrophilic polymer coating.
Mueller and Kliener, U.S. Pat. No. 4,136,250, disclose polysiloxane hydrogels and suggests the use of the same in contact lenses. These materials are also disclosed as capable of acting as drug carrier implant materials. The polymers are essentially hydrophilic olefinic polymer with a minor amount of hydrophobic siloxane.
Tanaka, et al, U.S. Pat. Nos. 4,139,513 and 4,139,692 disclose soft contact lenses composed of a hydrophilic moiety and a methyldi(trimethylsiloxy)sylylpropylglycerol methacrylate. These lenses are said to lie intermediate silicone rubber and conventional hydrophilic contact lenses in wettability and oxygen permeability.
Ellis, U.S. Pat. No. 4,152,508, discloses contact lens materials comprised of particular siloxanyl alkyl esters which are reported to be machinable and have high oxygen permeability.
Deichert, U.S. Pat. Nos. 4,153,641 and 4,189,546, disclose polysiloxane based polymers which are end-capped with activated unsaturated groups which have a polymerizable double or triple bond, typical of which are 2-cyanoacryloxy, acrylonitryl, acrylamido, acryloxy, methacryloxy, styryl, N-vinyl-2-pyrrolidinone-3-yl, N-vinyl-2-pyrrolidinone-4-yl and n-vinyl-2-pyrrolidinone-5-yl.
Chang, U.S. Pat. No. 4,182,822, discloses contact lenses comprised of a polymer formed from, inter alia, polysiloxanylalkyl ester of acrylate or methacrylate, of the class described by Gaylord, supra, copolymerized with N-vinyl pyrrolidone or N,N-dimethyl methacrylamide.
Novicky, U.S. Pat. Nos. 4,216,303, 4,242,483 and 4,248,989 discloses contact lenses comprised of high molecular weight polysiloxanylalkyl esters of acrylic and methacrylic acids, one such polymer including the substituent pentamethyldisiloxane.
LeBoeuf, U.S. Pat. No. 4,246,389, discloses acrylic siloxane based polymers, also containing HEMA and or polyvinyl pyrrolidone which are said to be suitable for use in forming water containing oxygen permeable contact lenses.
While the chemistry, vis-a-vis reaction conditions, of silicone hydrides is known and reasonably well understood, it has not, to the inventor's knowledge, been proposed to use such materials as contact lenses. In particular, the unique characteristics of such contact lenses has not been reported, insofar as is known to the inventor.